Process of bending laminated metal sheet

ABSTRACT

This invention improves on the process of bending in a conventional progressive stamping press a flat laminated metal sheet around a corner edge of a die block to form a generally straight piece-part corner, and comprises the steps of forming extended concavely rounded depressions in the opposite sheet faces at the sheet locations of the intended corner, then locating and clamping the sheet with the depressed regions aligned along a die block corner, and then mechanically bending the sheet with said depressed sheet regions aligned over the die block corner edge. The sheet depressions can be aligned essentially opposite one another, being rounded concavely and of a high width-to-depth ratio and of a depth to reduce the sheet to between 80-30% of its original thickness. The sheet depressions might occur at one stamping press station by opposing press tools each having a convex rounded working edge elongated along the length of the intended corner, with the blank bending occurring at a subsequent stamping press station.

BACKGROUND OF THE INVENTION

[0001] It has long been common to enclose physical components, such as electrical or electronics controls, mechanical pumps, valving, cooling fans and powering electric motors, or the Like, in a formed sheet metal housing having rigidity and strength for protecting the enclosed components. Use of conventional progressive stamping presses has been a favored manner of fabricating three-dimensional metal parts including housings, particularly when a great number of pieces are to be made, as a continuous web or blank of material can be used in making up all or a major portion of the part, for reducing inventory and the time and effort of assembling different parts. Progressive fabricating operations will be performed at sequential stamping stations, such as for shaping ribs, bosses, etc. on the blank surfaces, and/or for cutting, shearing or piercing through the blank for yielding needed holes or the overall blank shape, and/or for folding the blank to a general three dimensional part shape, and ultimately for shearing the folded and shaped piece from the blank. Each stamping station will thus have specifically configured but otherwise generally conventional punch/die assemblies that cooperate to achieve the above noted and possibly other fabricating procedures.

[0002] Specifically, a typical stamping press might have a base and ram powered to move toward and away from one another, with cooperating die and punch assemblies being respectively carried thereon at each stamping station and cooperating pin-bushing structures providing accurate reciprocating stamping strikes. A stripper plate is also carried by the ram guided to move in a direction substantially parallel to the punches, and being spring bias to a position with the punches essentially retracted behind the stripper plate remotely of the die assembly and die assembly blocks thereon. With the base and ram fully separated, the web or blank can be moved with clearance between the adjacent stripper plate and die blocks, being indexed with equal advances and stopped with the same blank portions in registry with the spaced stamping stations. To provide registry, pilot holes pierced in the stopped blank at a first stamping station receive pilot pins at each successive stamping station. The advancing web could be elevated slightly above the die blocks by spring biased lifters engaging the web side edges. Upon the ram-base closing, the stripper plate engages the web and holds it under the spring forces against the die blocks face, while subsequent continued ram-base closure protrudes the punches through stripper plate openings to effect a punch hit against the blank and die blocks. Bottoming blocks between each cooperating set of adjacent punch and die assemblies limit the punch-die block penetration. The reverse ram-base movement separates the punches from the die assemblies, spring lifters separate the blank from the die blocks, and the rising spring biased stripper plate strips the punches from the blank. Any blank portions severed during the stamping procedure, including both scrap and stamped piece-parts, can pass to an underlying collection bin or take-away conveyor for later recovery.

[0003] To reduce the needed power of the stamping press in having the punches pass through and/or deform the web material, the punches at the different stamping stations might be set at different heights to sequentially strike the blank.

[0004] When press folding a blank, the fold panel first will be die cut to have its perimeter free, while it yet will be coplanar with and cantilevered away from the main panel. The region where the blank is to be folded will be positioned to overlie a die block corner exteriorly shaped the same as the intended interior blank corner and fold panel angle, with clearance space underlying the fold panel. The main panel will be clamped between the stripper plate and die blocks, and a punch shaped generally the same as the fold panel, in the stamping stroke will engage the fold panel and force it around the die block corner and into the clearance space and possibly against the side of the die block. A punch lip can engage the blank corner exterior, between the main and fold panels, for improved corner retention at the folded angle.

[0005] While some advantages of conventional metal housings have been noted, a realized negative is that such housings will transmit or even amplify the noises of the housed components, or might even vibrate and create its own noises. This noise transmission aspect of course holds true for other sheet metal parts, so the invention to be disclosed herein might be advantageously applied for the stamping fabrication of them.

[0006] A modified form of sheet material, known as laminated metal, has been found most suited for reducing the transmission of noise or vibrations. This laminated metal is comprised basically by two metal sheets that sandwich and are held separated but relative to one another by a bonding elastic or vicoelastic material. One form of such laminated metal is sold under the trademark QUITE STEEL by MSC Laminates and Composites, Inc. of Elk Grove, Ill. The theory of providing reduced sound transmission is that the vibrational energy is converted into heat energy by the shear deformation of the vicoelastic core.

[0007] While the laminated metal housing and/or piece part made therefrom will effectively reduce noise or vibration transmission, the shaping or bending of the laminated metal, from a flat piece, to the desired three dimensional housing or any other intended part shape, by a conventional sheet metal stamping or progressive die press has been unexpectedly difficult, unreliable or even unacceptable. For example, bending the thin cross-section laminate material (of steel or possibly other metals) into a three-dimensional piece, has tended to shift the metal sheets relative to one another and along the sandwiched bonding elastic or vicoelastic material. Such sheet shifting could raise cosmetic concerns at visible misaligned sheet edges, and/or could create functional tolerance problems of location and/or size of holes, for example, due to misaligned sheet edges at the holes previously punched through the sheets. Further, sheet separation has been experienced at the edges, and/or internal stresses created in the laminated sheets on both sides of the formed corner has bowed or otherwise distorted the panels from being planar, as intended. The offshoot is potential customer rejection of the formed housing or component piece-part.

SUMMARY AND OBJECTS OF THE INVENTION

[0008] This invention relates to the process of shaping or bending a laminated metal web or blank, by means of a conventional progressive stamping press or folding technique that bends the flat blank or sheet over and around a corner edge of a supporting block or the like to form a generally straight corner.

[0009] An object of the invention is to improve the conventional stamping techniques or process to avoid misalignment of the exposed bent sheet edges and/or separation of the sheet laminates from the sandwiched adhesive therebetween and/or residual bowing of intended planar flat sheet portions or panels adjacent the formed corner or between adjacent formed corners.

[0010] A basic feature of the improved process of bending a laminated metal sheet, includes deforming the laminated metal to reduce the sheet thickness along the extended location of the intended corner, and thereafter mechanically bending the laminated metal sheet at said reduced sheet thickness location according to conventional press and/or sheet bending techniques.

[0011] A more detailed feature of this invention is to deform the laminated metal web or blank by depressing its opposite faces at locations essentially opposite one another, to reduce the sheet thickness greatest at what should be the center of the anticipated corner to be formed. This might be done at one press station with the web or blank generally planar by opposed press tools, each having a convex or rounded working edge elongated along the length of the intended corner, striking against the opposite sheet faces.

[0012] A suitable forming press tool might have a convex protrusion having a curvature radius between being approximately equal to and several times the original sheet thickness; and each face might be depressed between possibly 10-35% of the original sheet thickness, leaving the thinnest part of the web possibly between 80-30% of the original sheet thickness. The convex shape of the cooperating tools and the extent of the concave deformations provide that the greatest sheet depression occurs across opposed arcuate curvatures, although minor bulges might occur above the face of the blank immediately adjacent the ends of each depressed region, and further seem to confine all blank bending in these regions and virtually eliminates laminate sheet sliding or shifting in the blank regions laterally adjacent the depressions.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The above objects, advantages and features of the invention will be more completely understood and appreciated upon reviewing the following specification, the accompanying drawings being a part thereof, wherein;

[0014]FIG. 1 is a sectional view of a typical laminated metal sheet (or blank), with opposed crease regions or impressions formed therein;

[0015]FIG. 2 is a sectional view of punch or tool components for forming the crease regions in the FIG. 1 metal sheet;

[0016]FIG. 3 is a plan view of a flat blank illustrating the crease regions needed to form the piece-part of FIG. 4;

[0017]FIG. 4 is a perspective view of the piece-part formed from the blank of FIG. 3, practicing the invention; and

[0018]FIGS. 5 and 6 are cross sectional views of successive typical blank folding stations, showing cooperating punch and die components as used in folding the blank of FIG. 3.

DESCRIPTION AND EXPLANATION OF THIS INVENTION

[0019]FIG. 1 shows a sectional view of a piece 10 of laminated metal, being comprised of two metal sheets 12, 14 that sandwich and are held separated but relative to one another by a core 16 of a bonding elastic or vicoelastic material. The figure also shows typical crease regions or depressions 18, 20 formed in the opposite faces 18F, 20F of the laminated metal piece, according to the teachings of this invention.

[0020] More specifically, FIG. 3 shows in plan view a blank 22 which might be folded to three-dimensional piece-part 24 illustrated in FIG. 4. The piece part 24 has main panel 26, and opposed side panels 28, 30 (30 being shown only in FIG. 4), and side panel 32 folded 90 degrees from the main panel across corners 29, 31, 33 respectively; and further has flange panel 34 folded 90 degrees from the side panel 32 across corner 35.

[0021] The invention provides that prior to bending the fold panels 28, 30, 32, 34 relative to its adjacent hinged panel, crease regions or depressions 18, 20 will be formed in the opposite faces 18F, 20F of the laminated metal blank 22 along what will be the respective corner 29, 31, 33, 35 between the panels, as indicated by the dotted depression lines 29D, 31D, 33D, 35D in FIG. 3. The depressions 18, 20 can be made at any stamping station prior to bending the defined panels; as typically the miscellaneous holes or openings 40 will be punched in the blank 22 before panel folding.

[0022] Even after the crease regions or depressions 18, 20 have been formed at the 29D, 31D, 33D, 35D locations, the blank 22 will be substantially flat and each panel will yet be integral and coplanar with the adjacent panel(s) across each crease region or depression where each corner will be folded. Further though, the fold panel will be die cut to have free perimeter edges spaced from the anticipated fold regions and corners.

[0023] In forming the crease regions or depressions 18, 20, opposing punch and die components 40, 42 (FIG. 2) will be provided at one press stamping station “A” prior any subsequent blank bending stamping station(s) “B” (FIG. 5) and “C” (FIG. 6). Each punch and die component 40, 42 can be shaped as a protrusion 44 extended substantially along the entire intended corner length and terminating across a rounded converging end. As illustrated, the protrusion end might be curved convex and even of uniform curvature radius, which might be sized between being the same as and up to several times the sheet thickness. The punch and die components 40, 42 can be mounted to essentially oppose one another, and be moved toward one another without touching, operable to create the shallow depressions or concave valleys 18, 20 (FIG. 1) in the opposite blank faces at locations or regions essentially opposite one another.

[0024] Each depression or valley 18, 20 might be of generally uniform concave curvature, although they need not be at the same curvature; but preferably each will be much wider than its depth. This provides that the greatest reduction of sheet thickness would be near or at the middle of each valley near or at the center of the intended corner. Further, each depression face will blend then along a concave curve to near its opposite ends, where it might traverse across non-controlled small convex bulges before blending with the planar faces 18F, 20F of the laminated metal blank. The high width-to-depth ratio of the defined depression regions or valleys, with the greatest blank depression being between adjacent regions of lesser depressions, seems to confine virtually all panel bending at the intended corner and within the depressed regions; effectively then for substantially eliminating lateral sliding of the laminate sheets 12, 14 relative to one another beyond the depressions.

[0025] By way of example, a laminated metal blank 10 having a 0.042 inch thickness, formed of two steel sheets 12, 14 each of 0.020 inch thickness and a 0.002 inch resilient core 16, might be deformed by similar 3 mm tool components 40, 42 having a 0.060 inch radius convexly curved die. Further, each blank face might be depressed approximately between 10-35% of the original blank thickness, leaving the thinnest part of the web or blank possibly between 80-30% of the original blank thickness, or possibly between 0.015-0.035 inch thickness. With such tooling and depression formations, the width of each created concave valley might be at least twice and up to many times the valley depth.

[0026] The laminated metal blank 10, as so prepared with the extended depressed regions 18, 20 lying across the blank where the corner folds are to be made, can thereafter be indexed to a subsequent press station “B” (FIG. 5) or “C” (FIG. 6), where the depressed fold regions will be lined up substantially at die block corner edges (50 in FIG. 5, or 60 in FIG. 6) of supporting press die blocks 52, 62 respectively. When so positioned, holding blocks (52, 53 in FIG. 5 and 62, 63 in FIG. 6) opposing the main blank panel (26, 32 in FIG. 5, and 26 only in FIG. 6) can effectively clamp the blank in the press, and the fold panel (34 in FIG. 5 and 32 in FIG. 6) will be integral and coplanar therewith across the depression region and cantilevered to underlie (FIG. 5) or overlie (FIG. 6) adjacent clearance space (55 in FIG. 5 and 65 in FIG. 6). The press folding punch (56 in FIG. 5 and 66 in FIG. 6) might then be moved relative to and against the cantilevered fold panel for bending it around the die block corner edge and into the adjacent clearance space and possibly against the side face of the die block. The die block corner edge might be slightly rounded convexly and the punch might have a rounded Lip (58 in FIG. 5 and 68 in FIG. 6), operable to engage the opposite blank faces to help set the size, shape and angle of the intended corner to the required specifications.

[0027] The above noted stamping press fixtures and techniques can be standard or conventional, except for the inventive tooling and step of first preforming the blank to be folded with the corner depressions and then appropriately aligning such depressions at the die block corner edge, before actually bending the blank.

[0028] It should be noted that the above added preforming steps have unexpectedly improved bending results in that post-formation visual examinations of all formed corners made with this process reveal that the panels adjacent the corner remain flat and planar, and the exposed laminate edges of the fold panels remote from the formed corner were yet sharp and square; indicating virtually no lateral shifting of the different metal sheets occurred during the otherwise conventional stamping formation of the bent corners.

[0029] The process is not limited to only laminate metals of steel, as metal laminates can be made of other metals; and the metal sheets need not be of the same thickness.

[0030] While only a single embodiment is illustrated, changes thereto or modifications therefrom can be made by a person skilled in the art. Consequently, the scope of the invention is to be limited only by the following claims. 

What is claimed is:
 1. A method of folding, with a conventional stamping press, a generally flat laminated metal sheet about a corner to form a three-dimensional piece, the combination comprising the steps of: locating the sheet at a first press station, and striking a press tool having a convexly rounded working edge elongated substantially along the entire length of the intended piece corner against a sheet face at the location of said intended piece corner, for forming an elongated concavely rounded depressed region therein and thereby reducing the sheet thickness between adjacent main and fold sheet portions; locating the sheet at a second press station to have the main sheet portion supported on a press block with the depressed region aligned adjacent a press block corner and the fold sheet portions cantilevered beyond the press block corner to an adjacent clearance space; and holding the main sheet portion against the press block while moving a folding tool against the fold sheet portion for bending said sheet about the press block corner at the depressed region.
 2. A method of folding a laminated metal sheet according to claim 1, further wherein opposed striking press tools are used for forming concavely rounded depressed regions in the opposite sheet faces at essentially opposite locations proximate said intended piece corner operable for reducing the sheet thickness between the adjacent main and fold sheet portions.
 3. A method of folding a laminated metal sheet according to claim 2, further wherein each depressed region is of a generally uniform curvature having a radius sized between the same as and up to several times the sheet thickness.
 4. A method of folding a laminated metal sheet according to claim 2, further comprising each depressed region having a depth between 10-35% of the original blank thickness, leaving the thinnest part of the sheet at the intended corner between 80-30% of the original sheet thickness.
 5. A method of folding a laminated metal sheet according to claim 2, further wherein each depressed region has a high width-to-depth ratio, the width being at least twice and up to many times the depth.
 6. A method of folding a laminated metal sheet according to claim 4, further wherein each depressed region is of a generally uniform curvature having a radius sized between the same as and up to several times the sheet thickness.
 7. A method of folding a laminated metal sheet according to claim 6, further wherein each depressed region has a high width-to-depth ratio, the width being at least twice and up to many times the depth.
 8. A method of folding a laminated metal sheet according to claim 2, further wherein each depressed region is of a generally uniform curvature having a radius sized between the same as and up to several times the sheet thickness, and each depressed region having a depth between 10-35% of the original blank thickness, leaving the thinnest part of the sheet at the intended corner between 80-30% of the original sheet thickness.
 9. A method of folding a laminated metal sheet according to claim 2, further comprising each depressed region having a depth between 10-35% of the original blank thickness, leaving the thinnest part of the sheet at the intended corner between 80-30% of the original sheet thickness, and each depressed region having a high width-to-depth ratio, the width being at least twice and up to many times the depth.
 10. A method of folding a laminated metal sheet according to claim 2, further wherein each depressed region being of a generally uniform curvature having a radius sized between the same as and up to several times the sheet thickness, and each depressed region having a high width-to-depth ratio, the width being at least twice and up to many times the depth.
 11. A method of folding, with a conventional stamping press, a generally flat laminated metal sheet about a corner to form a three-dimensional piece, the combination comprising the steps of: forming opposed elongated concavely rounded depressed regions in opposite sheet faces substantially along the entire length of and at the sheet location of the intended piece corner and between adjacent main and fold sheet portions; supporting the main sheet portion on a press block with the depressed region aligned adjacent a press block corner and holding it there, and moving a fording tool against the fold sheet portion cantilevered beyond the press block corner to an adjacent clearance space for bending said sheet about the press block corner at the depressed region.
 12. A method of folding a laminated metal sheet according to claim 11, further comprising each depressed region being of a generally uniform curvature having a radius sized between the same as and up to several times the sheet thickness, each depressed region having a depth between 10-35% of the original sheet thickness, leaving the thinnest part of the sheet at the intended corner between 80-30% of the original sheet thickness, and each depressed region having a high width-to-depth ratio, the width being at least twice and up to many times the depth. 